398 
THE PRINCIPLES OF BOTANY. 
wards occupy a considerable space. Thus the produee of a 
single flower of the following plants would be as under: 
Seeds. 
Sow Thistle ..... 150 
Groundsel ...... 150 
Yellow Toadflax . . . .118 
Foxglove ...... 800 
Broomrape ..... 1,000 
Couple with these facts also the one that some of the 
common plants produce their seeds from seed in a few weeks, 
and may, indeed, have two or three generations in a season, 
and we have a solution to the eommonly repeated story that 
from however deep you dig up soil, as from wells and mines, 
you bring up weed seeds, the truth being, wherever we have 
investigated these assertions, that one or two seeds have 
developed an unnoticed plant or plants, and as these have 
seeded on a fresh soil their rapid and complete growth of 
almost every seed is secured. This subject like that of the 
asserted longevity of seeds is one which requires rigid serutiny 
before we assent to all that has been advanced. Experiment 
has shown us in the ease of wheat sowing that the best 
results are obtained at two inches, but below four searcely 
ten per cent, of the seed will eome up; of the non-germi¬ 
nating most of it soon dies, but some would maintain its 
vital powers for many months. In nature, seed of eourse, is 
sown on the surface of the soil, in which case much of it is 
lost from various causes. In experiment it is buried, and so 
far screened, and, according to the experiments of Petri, 
beyond the depth of one inch, with a fast decreasing pro¬ 
portional of germinal power. 
Table of the Germination of Seeds. 
Seeds sown to the 
depth of 
Came above ground 
in daj'S. 
Number of plants that 
came up. 
^ inch. 
n 
Seven eighths. 
1 ,, 
12 
All. 
2 inches. 
18 
Seven eighths. 
3 „ 
20 
Six eighths. 
4 „ 
21 
Four eigliths. 
5 „ 
22 
Three eighths. 
6 „ 
23 
One eighth. 
Temperature has a great deal to do with germination ; thus 
during the present spring we have had some oats several 
